The present invention relates to a distribution type fuel injection pump for use in an internal combustion engine, such as a diesel engine.
In conventional distribution type fuel injection pumps wherein a plunger is mounted on a barrel so as to be capable of reciprocal axial movement to suck and to pressurize a fuel and rotate about its axis to distribute the pressurized fuel to each combustion chamber of the engine, an injection timing apparatus (so called engine speed timer) is disposed. The injection timing apparatus automatically advances the injection timing in accordance with an increase in the engine revolutions, i.e. engine speed.
On the other hand, in an injection type internal combustion engine, such as a diesel engine, in order to easily start the engine, it is necessary to advance the injection timing at the time of the engine starting operation. That requirement is more important in a cold engine condition.
Accordingly, in the conventional injection timing apparatus, an auxiliary injection timing adjusting means for advancing the injection timing at the time of the engine starting operation has been employed. The auxiliary injection timing adjusting means taught by an invention cited in the Japanese patent application No. Sho 53-133561 (Japanese publication No. Sho 55-49078) filed in the Japanese Patent Office by an applicant of this present invention is one of the most available means for advancing the injection timing at the time of the engine starting. That means teaches the follows. The distribution type fuel injection pump comprises a cam member causing the plunger to reciprocally move while the plunger rotates to distribute the fuel into each combustion chamber of the engine. The angular position of the cam member about its axis can be controlled by a timer piston operable as the fuel injection timing control means to advance the fuel injection timing in response to the engine speed. The cam member also turns about its axis so as to be adjusted in its angular position by an auxiliary piston disposed on the same axial line as that of the timer piston. The auxiliary piston causes the timer piston to adjust to advance the fuel injection timing at the low engine speed, for example at the time of engine starting.
When the above-mentioned conventional arrangement is adopted, the intended object can be attained if the engine temperature is low at the time of engine starting. The starting injection timing, however, is held even at the time of engine restarting in the warming-up state where maintenance of the starting injection timing is not especially necessary. Accordingly, the content of NOx components in the exhaust gas is increased, and abnormal combustion such as knocking is caused thus increasing the noise of operation.